SSkindog

Is it the tranny low gear ratio X the rear end gear ratio?
Or do you add them together to come up with SLR?

And what, if any is the ideal SLR for drags?

OldSStroker

Gears MULTIPLY torque. You were correct; trans ratio x axle ratio.

Optimum 'SLR' as you call it depends primarily on traction available.


You might want to post this on the "Drag Racing" forum (before it gets moved).

Injuneer

Moving...... .

Stephen 87 IROC

Ideal low ratio depends on how much torque the engine can produce and how good the traction is.

Lets use 2 engines. A V6 with 300 pounds of torque and a V8 with 400 pounds of torque. Both will use a 700R4 with the 3.06 first gear. The V6 will have 3.73 gears in the diff and the V8 will have 2.73 gears. Both will use the same tire size and because of options in the cars they both weigh the same.

V6 = 3.06 x 3.73 x 300 = 3424.14 pounds of torque at the rear wheels.
V8 = 3.06 x 2.73 x 400 = 3341.52 pounds of torque

The V6 will be slightly quicker off the line with the extra 82 pounds of torque. It would probably fall back before the 60' mark since the V8's engine torque will quickly out accellerate the V6.

By simply changing the gear ratio, you can increase the amount of torque going to the rear wheels but having too much will spin the tires and not go anywhere.

If the V8 car swapped the tranny for a TH350 for a closer ratio gear set to get away from that very low first gear and changed the rear gear to 3.73 it would then have 3759.84 pounds of torque at the wheels and would be noticably quicker.